As of today, an estimate of Bitcoin’s carbon footprint has been added to the Bitcoin Energy Consumption Index. Many readers requested for the addition of this number, as it gives a more detailed understanding of Bitcoin’s environmental impact. This impact is significant, as the electricity going into the Bitcoin network is mostly coal-based. This type of electricity has an emission factor of up to 1 kg CO2e per kilowatt-hour (KWh).
The estimate featured on the Bitcoin Energy Consumption index applies a more conservative emission factor to the network, based on the emission factor of China’s national electricity grid (including electricity from other sources) of around 0.7 kg CO2 per KWh, for only 70% of the total electricity consumed by the network (the remaining 30% is assumed to be based on clean energy).
The resulting estimate can be found here.